Recovery of azeotropic former in distillation of hydrocarbons



.5. WHWNHQUSE 2,435,192 0F ZEOTROPIC FORMER IN DISTILLATION 0FHYDROCARBONS Fd@ W?.

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Patented Feb. 4, 1947 RECOVERY oF AzEoTRoPIC FORMER lIN DisTiLLATroN oFHYDRoCARBoNs John D. Rittenhouse, Palos Verdes Estates, Calif., assignorto Union Oil Company of California, a corporation of CaliforniaApplication October 18, 1941, Serial No. 415,589

11 Claims. 1

This invention relates to a process of azeotropic distillation tovprepare pure hydrocarbons from complex petroleum fractions which arediiicult to separate by ordinary fractional distillation due to thesmall diiferences in boiling points of the hydrocarbons contained in thepetroleum fraction. The invention is particularly directed to animproved process for separating the hydrocarbons and the azeotropeformer that are contained in the azeotropic distillate produced by theazeotropic distillation.

The process of separating one hydrocarbon component from anotherhydrocarbon component of substantially the same boiling point containedin a. complex hydrocarbon fraction by azeotropic distillation is wellknown. This process consists in distilling the hydrocarbon fraction inthe presence of an extraneous substance which has a preferential anityfor one of the components contained in the complex hydrocarbon fraction,thus causing a disturbance of the vapor pressure equilibrium thatformally existed in the fraction in such a manner that the partial vaporpressure or fugacity of at least one component in the'fraction ischanged suiciently to permit its separation by controlled fractionaldistillation. In such processes, the distillation effects the separationof the relatively more paramnic hydrocarbons together with extraneoussubstance leaving as undstilled bottoms the relatively less paraillnichydrocarbons which may or may not contain a portion of the extraneoussubstance. In the present description of my invention the aforesaid typeof fractional distillation will be referred to as azeotropicdistillation,

the extraneous substance or substances which are added to the complexhydrocarbon fraction to eifect the aforementioned change will bereferred to as azeotropic formers andthe overhead from the azeotropicdistillation will be referred to as the azeotropic distillate.

One of the main diiculties in the azeotropic distillation process is inthe separation or recovery of the azeotrope former from the hydrocarbonscontained in the azeotropic distillate. One of the methods proposed forthis purpose resides in washing the' azeotropic distillate with waterwhich is adapted to dissolve the azeotrope former from the azeotropicdistillate and thus be separated from the hydrocarbons by settling andstratification. The solution of azeotrope former and water may bedistilled to separate the azeotrope former from the water.

However, difculty has been experienced to separate the azeotrope formersubstantially completely from the azeotropic distillate by washing withwater since in many cases, the azeotrope former has a preferentialsolubility in the hydrocarbons as compared with the solubility in thewater. The result is that the hydrocarbons must be washed with anexcessively large amount of water in order to remove the last traces ofthe azeotrope former so that the hydrocarbons may be utilized and theazeotrope former recovered without sustaining a substantial loss of thismore valuable material. To illustrate, it has been found that methylethyl ketone, particularly containing about 10% by volume of Water, is avery eiiicient azeotrope former to effect the separation of non-aromatichydrocarbons from a hydrocarbon fraction containing toluene. Yet the useof this azeotrope former offers the serious diiculty of recovering themethyl ethyl ketone from the azeotropic distillate. W'hile theseparation of the methyl ethyl ketone may be accomplished by washingwith Water, this has required about five or six volumes of water foreach volume of azeotropic distillate. Even by washing the azeotropicdistillate with this large amount of water, the hydrocarbon thusseparated still contained about one percent of methyl ethyl ketone.Furthermore, in order to recover the methyl ethyl ketone from the verydilute Wash solution, it is necessary to heat an excessively largevolume of dilute methyl ethyl ketone-water solution.

It is thus an object of my invention to effect a substantially completeseparation'of the azeotrope former from the hydrocarbons contained inthe azeotropic distillate and it is a particular object to effect theaforesaid separation in an efficient and economical manner without lossof azeotrope former.

It is a further object of my invention to effect the separation of the`azeotrope former from the azeotropic distillate by the use of selectiveabsorbents having a preferential absorbing power for the azeotropeformer than for the hydrocarbons contained in the vaporized azeotropicdistillate. A further object is to eifect the sepal ration while theazeotropic distillate is in the vapor phase and the selective absorbentis in the liquid phase.

I have discovered that a substantially complete separation of theazeotrope formers from the vaporized azeotropic distillate may beaccomplished by the use of absorbents having a preferential absorbingpower for the azeotrope former than for the hydrocarbons. Thus, theseparation according to my invention may be acoomplished by simplyintimately contacting the vaporized azeotropic distillate with asuicient amount of selective absorbent at a suitable temperature toenable the selective absorbent to absorb or extract the vaporizedazeotrope former from hydrocarbons and allowing the vaporizedhydrocarbons to be withdrawn as an overhead vapor while the azeotropeformer dissolved in the absorbent is removed as a liquid from the bottomof the extractor or absorber.

To illustrate the advantage of employing a selective absorbent forelecting the separation of the azeotrope former from the azeotropicdistillate, a vaporized azeotropic distillate of hydrocarbons and methylethyl ketone of identical cornposition as that described above which waswashed with water, was countercurrently contacted with about threevolumes of the diethylene glycol to one of the azeotropic distillatemeasured as liquid, The extracted hydrocarbons thus recovered whencondensed were substantially free from methyl ethyl ketone. Thus. it ispossible by my invention to produce a hydrocarbon fraction which is freeof azeotrope former by employing a considerably less amount of theselective absorber than when the azeotropic distillate is extracted withwater. f

Besides diethylene glycol mentioned above, selective absorbents which Ihave found suitable to eiect the extraction of azeotrope formers fromazeotropic distillates include phenolic compounds such as resorcinol,parachlorophenol, phenol, xylenol, pyrogallol, pyrocatechol, diandtri-hydroxy toluene, tetrahydroresorcinol and pyrogallol, cresylic acid,polyhydric alcohols such as mono, tri, tetra and hexa-ethylene glycolsand dipropylene glycol, amines such as mono, di, and tri-ethanolamine,2inethyl propanol amine, diethylene triamine, triethylene tetramine,tetraethylene pentamine, diethylene diamine, trlethylene triamine,diphenylamine, Xylidme, aniline, ortho phenylene diamine, alpha naphtholamine and phenyl hydrazine, fatty acids such as acetic, propionic andformic acids and glycolic acids, cyclic ketones such as cyclohexanone,alkyl ethers of polyglycols such as mono-ethylether of diethyleneglycol, ethyl ether of ethylene glycol,

heterocyclic compounds such as' furfuryl alcohols, tetrahydro furfurylalcohol, nitro-parafns such as nitropropane, aromatic compounds such aspoly nitrohenzenes, benzyl alcohol, benzonitrile and benzyl luorides,efhers such as BB dihydroxy ethyl ether and para nitro diphenyl ether,aliphatic nitriles such as propiom'trite, aliphatie iiuorides such ashexo luoro ethane.

Gf the above selective absorbents, I have found such compounds asresorcinol, phenol, pyrogallol,

. pyrocatechol, BB dihydroxy ethylether, mono,

di, trie, tetraand hexanonaethylene glycol, di-` prop'ylenc glycol,propylene glycol, phenyl hydrazine, para chloro-phenol, para nitrodiphenyl other and acetic acid to be particularly suitable lorseparating such azeotrope formers as such ketones as acetone, methylethyl ketone, alcohols such as methyl ethyl and isopropyl alcohols,

CII

4 dioxane and morpholine from non-aromatic hydrocarbons having a boilingrange of 200 to Azeotrope formers which may be separated ac- I cordingto my invention from azeotropic distillates produced by azeotropicdistillation include all of the compounds disclosed above as selectiveabsorbents for separating the azeotrope former from the azeotropicdistillate. However, in effecting a separation of the azeotrope formerfrom an azeotropic distillate, it is obvious that the same materialsshould not be employed as a selective absorbent as was employed to electthe azeotropic distillation. Whether a particular material will functionas a selective absorbent to separate the azeotrope former from theazeotropie distillate depends upon the character of the azeotropicdistillate such as the boiling point and solubility characteristics ofthe hydrocarbons and of the azeotrope former contained therein. Forexample, a compound may be ecient to perform the azeotropic distillationto separate hydrocarbons from a particular complex hydrocarbon fractionand may be ineiiicient to separate hydrocarbons from a complexhydrocarbon fraction of a different boiling point; yet this samecompound may be useful as a selective absorbent to separate a differentazeotrope former from the azeotropic distillate produced from suchcomplex hydrocarbon fraction of different boiling point. To illustratespecically, tetra ethylene glycol is a particularly elcient azeotropeformer for separatng relatively paramnic hydrocarbons in the lubricatingoil boiling range from the relatively nonparanic oil fractions and is ofless efllciency for separating non-aromatic hydrocarbons from a toluenefraction. However, the tetra ethylene glycol is an efficient selectiveabsorbent for removing an efficient azeotrope former such as methylethyl ketone from the azeotropic distillate obtained from the azeotropicdistillation of a toluene fraction.

In selecting a selective absorbent for theseparation of azeotrope formerfrom a particular azeotropic distillate, it is preferable to choose onewhich has a materially higher boilingpoint than that of the azeotropeformer so that the selective absorbent may be maintained in the liquidphase during the absorption and the subsequent separation of theazeotrope former and selective absorbent frorn each other may be readilyaccomplished by simple fractional distillation.

In general, when desiring to separate nonaromatic hydrocarbons fromaromatic hydrocarbons, the azeotropic distillation is controlled todistill all non-aromatic hydrocarbons together with azeotrope former,leaving as bottoms the aromatic hydrocarbons which may or may notcontain azeotrope former depending upon the quantity of azeotrope formeremployed. Depending upon the stock, the non-aromatic hydrocarbonscontained in the azeotropic distillate may consist of a mixture ofparaihn and naphthene hydrocarbons and it is another object of myinvention to separate these non-aromatic hydrocarbons into componentparts. In this connection, it is a particular object of my invention toseparate the azetrope former from the vaporized azeotropic distillate byselective absorption as herein described and then subject the resultinghydrocarbon vapor to solvent extraction with a selective solvent whichis adapted to extract the naphthene hydrocarbon vapors, leaving theparain hydrocarbons as an undissolved vapor.

The selective solvent extraction to separate the be extracted by theselective solvent.

paraflin from the naphthene hydrocarbons is preferably carried out bypassing the hydrocarbon vapor countercurrent to the selective solventwhile maintaining a temperature in the extraction column sufcientlyelevated to prevent the paran hydrocarbons from condensing, yetsuiiciently low to prevent the selective solvent from vaporizing.Preferably, a selective solventl is chosen which has a substantiallyhigher boiling point than the hydrocarbons so that vaporization of theselective solvent is eiectively prevented. Selective solvents for thispurpose include substantially all of the aforementioned selectiveabsor-bents but when a selective solvent is chosen which is the samecompound used for the selective absorption, a lower temperature andpreferably a higher pressure should be maintained than is employed inthe selective absorption process for separating the azeotrope former. Inother words, during the selective absorption step to remove theazeotrope former, the temperature of absorption should be sufficientlyelevated to prevent the hydrocarbons contained in the azeotropicdistillate from condensing or from being extracted by the selectiveabsorbent, yet sufficiently low to eiect the extraction of the azeotropeformer. If the temperature is maintained lower than such conditions, theselective absorbent will also extract hydrocarbons, such as therelatively more naphthenic hydrocarbons as well as the azeotrope former.During the selective solvent extraction step to separate the naphthenehydrocarbons from the parain hydrocarbons employing the same compound,the temperature must be maintained at a lower level, otherwise ifmaintained at a higher or equal level to that of the absorption step,the hydrocarbons will remain in the vapor state and hence will notHowever, by choosing a different compound for the selective extractionthan was employed for the selective absorption, it is possible,depending upon the characteristics of the compound such as its solventpower, to effect the extraction at the same, lower or higher temperaturethan employed during the selective absorption step. In some cases, theextraction of the naphthenic hydrocarbons may be accomplished byemploying a higher pressure even though the same temperature is employedas that employed for the selective absorption step. Selective solventswhich I have found particularly suitable include phenol, benzyl alcohol,nitrobenzene, aniline, phenyl ethanolamine, triethylene tetramine, paraphenetidine, triacctin, acetonylacetone, monoethyl ether of diethyleneglycol, tetrahydro furfuryl alcohol, furfural, diglycol diacetate,methyl ether of diethylene glycol, isopropanolamines,

dipropylene glycol, .benzyl and phenyl ether of ethylene glycol,nitrophenol, ethyl phenylethanolamine, ortho nitrochlorobenzene,propionitrile and epichlorohydrin.

Other objects, features and advantages of my invention will be apparentto those skilled in the art from the following description of theinvention which represents a diagrammatic arrangement of apparatus forcarrying out my invention. In the following example, the invention willbe described as applied to the separation of toluene from a hydrocarbonfraction employing methyl ethyl ketone containing about by volume ofwater as the azcotrope former for the recovery of the toluene anddiethylene glycol as the selective solvent for the extraction of theaeotrope former from the azeotropic distillate containing thenon-aromatic hydrocarbons.

However, it will be observed that this example is not to be taken aslimiting my invention since the process is applicable to separate othercomponents from complex substances employing other azeotrope formersunder conditions adapted to eiect the desired separation.

In the drawing, the hydrocarbon feed to be resolved intoV its componentparts, such as for example, a hydrocarbon extract fraction obtained bysolvent extracting gasoline with liquid sulfur dioxide, said fractionhaving a boiling range "of about 200 to 240 F. and consisting ofsubstantially 45% by volume of toluene, 20% by volume of parafnhydrocarbons and 35% by volume of naphthene hydrocarbons, is taken fromtank I0 via line I I and is pumped by pump I2 through line I4 controlledby valve I5 into line I6. Azeotrope former, such as methyl ethyl ketone,containing about 10% water, is taken from tank II via line I8 controlledby valve I9 and is pumped by pump 20 through lines 2| and 22 and valve23 into line I6 where it is mixed with the hydrocarbon feed from tankIIJ. The mixture of hydrocarbon feed and azeotrope former in the ratioof approximately two parts of the azeotrope former and one part ofhydrocarbon feed in the example herein given, is passed intofractionating column 24 wherethe mixture is subjected to fractionation,heat being supplied by closed steam coil 25. If desired, the azeotropeformer may be introduced directly into the fractionating column at anyother point as near the top of the column in which case it will actinpart as reflux `for the fractionation. In the fractionating column, thedistillation is controlled so as to distill overhead an azeotropcconsisting of the paraiiin, olefin and naphthene hydrocarbons togetherwith substantially all of the methyl ethyl ketone and water. In theexample herein given, this is accomplished at an overhead temperature ofapproximately 16C-170 F. and at atmospheric pressure. If desired, theazeotropic distillation may be carried out either at atmospheric orsuperatmospheric pressure or under a vacuum. The `above overhead mixtureis removed from the fractionating column via line 26, controlled byvalve 21 and may be heated or cooled in 28 and passed via line 29 intoline 30 controlled by valve 30a to the methyl ethyl ketone-watervrecovery system, as

4will be described hereinafter. In some cases, the

stantially the same composition as the uncondensed vapor. which may berecycled to the fractionating column to serve as reflux. This may beaccomplished by passing the partially cooled azeotropic distillate vialine 3I controlled by valve 3Ia into a separator 32 from which thecondensate may be recycled by line 33 controlled by valve 33a and pump32a to the iractionating column 24. The uncondensed vapors are removedvia line 34 controlled by valve 35 and passed into line 30.

The bottoms in the fractionating column 24 consisting of thearomatic'fraction of toluene are withdrawn via line 3G controlled byvalve 3l and are pumped by pump 38 through line 39. lf the hydrocarbonfeed to the azeotropic distillation has been carefully fractionated toproduce a fraction free from aromatic hydrocarbons other than tolueneand if the azeotropic distillation has been carried out under suchconditions as to remove all of the non-aromatic hydrocarbons andazeotrope bottoms: are passed`r via `lines line 41 controlled by'valve48 -from which itpasses i through' heater/,49 and line 50 intofractionating "condensate maybe I ing tank by pump 51 and passed intoline .58. VIf desired, part of. the condensate may line 59 controlledbyvalve. 60 `to the fractionatfing'column'5l to serve as.- reflux fforthefractionation. The remainingfportion is passed via, line 6| icontrolledby valvef62 'through lineg 45 into storage tank 46.; The bottoms fromthe fractionating column,v consisting of .xylene or a mixture of xyleneand higher boiling varomatic hydr'ocarbons, is withdrawn via line-6 3controlled 'fractionating column "a'zeotrope Iformer',` this may beremoved by pass 'fingthe bottom i controlled by valve .69 through heater'HJ and line 1I 'into'fractionating column 12 provided .with a -heater13 Aand reflux cooling lcoil 1147..where the` l ywhich it may be umn 24by pump 19 and line 80 controlledfby valve v 8| and "lines 22' and 82'controlled by valve tank r46l and thev higher `perature of about'230"former, the bottoms the iractionating, umn-:ray be passed ,directlyvialines 36,39, 40

Acontr Jlled'. by -valve 4l 42 43 controlled byfvalve tand 45 intostorage tank 46..; However, in the `evr nt ithecharging fstock -hasI notbeen y carefully fractionated'to remove aromatic hydrocarbons l ,eavierthan toluene,rsu`chas-xylene,z etc.,V the bottoms inV the'fractionating" column 24 willvcontain all or substantial amounts ofsuch aromatic-hy- .drocarbons` `In theevent it is desired to recover'theiaromatic hydrocarbon mixture per se, it is :passed directly totanlr46 4as described above. However, if it'isdesired-to separate theltoluenefrom the remaining 7aromatic hydrocarbons, ythe .36, as, 40., 42` intocolumn `vi/here the-mixture is. lfractionated to remove the toluene asan overhead product aided byheat from the heater 52; Thevapo-rizedtouene is removed from the `:top of the fractionating columnV5I via line 53, condensed in condenser.` 54 and passed-viafline- 55into collecting tank 56,. l 'lhe withdrawn from the collectbecycledviaby valve 64 andA pumped byfpump 65 and line 66 into storage tank 61.

-In the' event the 24 contains a portion of the fractiongvia ,lines 36-139. and 68 azeotrope former may be fractionated* andre- Vmoved via line15, condensedin-condenser16and v11 into collecting tank 18 from returnedto the fractionating colpassed via line .|6. The bottomsffrom .theA 12may be passed-vialine 83. into line 42 `from kwhich it may be passed bypump -84 either directly to the storage tank 46. or to" fractionatin'g,column 5I in accordance With'the above disclosure.

Thev toluene ornthe mixtureof toluene and higher boilingaromatichydrocarbons obtained in boiling aromatic hyin tank 6.1 may be treatedfractionating column drocarbons obtained With clay which may v F.'employing 1 to ipounds of clay per barrel of the hydrocarbon fraction.

fractionation in fractionating column 5| in which cas'efthe-ractionationin 5l 'may serve 'either to rerun the clay treated stockand/or to fractionate the high boiling aromatic vhydrocarbons from thetoluene. In place of clay treatment, Vthe aromatic *fraction may becooled andrthen treated with 1 lto '10i pounds of sulfuric acidv per:barrel of the hydrocarbons followed by neutralizationwith clay`or'caustic alkali. The acid .treatment serves to remove small' tracesof undesirableunsaturated hydrocarbons which may-be detrimental in colorstability and nitration ofthe toluene.

In order to recover the azeotropeformer from bottoms fraction from thebe accomplished at a tem.

the azeotropi distillate,

v line-88 controlled by valve y i vpassesthe absfonbentfjthrough heater9| 'into-the permittingrthe hydrocarbons to' o o avapor substantiallylfree from Veither the selecsufficiently; elevated s o th .tiveabsorbentin the distillate `isgpassed inthe vapor'state into thebottomof the extractor orr absorber 85'pr'ovided yv vitl'r packing* materialsuch. as broken' me'l ssa andgrwith'heatef se where the vapors ariecountercurrently co'n'tacted"vvith selective absorbent "Withdrawn from'tank 81 via phase ofazeotrop'eformer and selectvefabsorbent is in theliquid-phase;

` 'In' orderto obtain-'this absorbent for the -azeocondition,l theselective point above `trope Vformer should have a boiling that ofthetemperature of extraction.f Thus,

when employing .diethylene glycol asthe lselecthe 'examplelier'elnfgivemthe temperature of extraction is preferably carried out`at 350 FI, employing approxir'natelyr` three fvolumes of theVAdiethylene' glycol"V to' one volume vof the azeotropicdistillate'measure'd as aliouid.

."InV So'rrlefcases, it.. may; be desirable to, eneetthe temperaturethan' underf l d A scribedabove, i. e., sufficiently l'o'w `toextract'v'the .tive absorbent.'` The '.drocarbons may then extractionwith` thel selective absorbent 'at `a lower the f conditionsprerelatively ,'.less vparafflnic hydrOcarbonis such as fthe naphthenehydrocarbons las' vvellv asl-#the azeotrope' former, leaving theparainnicjhydrocarbonsv as', vapors'. which' may then be" separated fromthe solution of relatively less, parainic hydrocarbons, azeotrope formerand selecrelatively lessparafnic -hyl be sepfllated from the solutionbycooling and stratiyi'ng the mixture which effects a rejection ofhydrocarbons vfromthe solu- .tiorr consisting fof non-aro- Theextract-ed vapor l from methyl ethyl kematlc hydrocarbons y free toneVand Water and selective: absorbent is lwithdrawnvia line 92w controlledby vpassed via valve 93 to lcondenser n 1 thecondensate passes via line95` into collecting 50.V

tank .96; `The 'condensate is pumped by pump y 91 andline V,98.lntostorage tank 99..

The .liquid extract phase consisting of methyl ethyl ketone, water andselective l' absorbent is withdrawn from thebottom'of the extractorl 85via-line -|rv00v.controlled by valve IUI andis pumped |62. through linelll?)s heater |64 line H15"r into fractionating .column IIJ6`v providedwith heater 1,01 Where the azeotrope former, l. e.,

' methyiethyl ketone Containing about-10% by Y*If desired, .the claytreatment may.precede. the

' controlled by valve volume ofjrwater is stripped from the selectiveabsorbent and passes via line l'c'ontrolled by valve |09 through lines22 'and' I6 into the fractionatln'glcolumn 24 in order to effecttherazeo- Atropicdistillation of the -hydroca rbonfeed..A The A may be.'passedvla line -H0 HI, condensed in condenser H2 rand condensatecollected-in collecting .tank H4 from whlchit isvwithdrawn byzpump H5,and a portion recycled-via line H6 controlled by valve H1 toYfractionating column .|06 to serve as reflux for the fractionation.,'Ivherernainlngcondensate maybe `passed via line H8 controlled bylvalve H9 into storage tank H1.H

The bottoms in fractionatin'g' column'l' 'conazeotropeformer sisting ofthe selective absorbent are withdrawn valve 93,A and 4and passes intothe top of the extractor 125.

via line 120 controlled by valve |21. and are pumped by pump 122 throughline 123 into storage tank 8l. t

As indicated above, the vapors from the extractor 85 may be extracted inthe vapor phase with a selective solvent in order to separate thesevapors into paramn hydrocarbons and naphthene hydrocarbons or into afraction which is` relatively paraiiinic and a fraction which isrelatively non-parafiinic. This is accomplished `by passing thehydrocarbon vapors from the extractor 85 through lines 92 and 124controlled by valve 125 into the bottom of the extractor 126 providedWith packing material such as broken tile 121 and heater 123 where thevapors are countercurrently cntacted with selective solvent withdrawnfrom tank 129 via line 130 controlled by valve |31 and pump 132 fromwhich the solvent In the extractor, the selective solvent extracts thenaphthene hydrocarbons from the vapor permitting the paraffinhydrocarbons to be separated as a vapor substantially free from eitherthe yselective solvent or naphthene hydrocarbons. The extraction ispreferably carried out at a temperature sufciently elevated so that theparain hydrocarbons remain in the vapor phase and the selective solventand naphthene hydrocarbons are in the liquid phase. In order to obtainthis condition, the selective solvent for the naphthene hydrocarbonsshould have a boiling point above that of the temperature of theextraction. Thus, when employing benzyl alcohol as the selective solventin the example herein given, the temperature of extraction is preferablycarried out at about 250 F. employing approximately three volumes of theselective solvent to one volume of the hydrocarbons measured as aliquid.

The extracted vapor consisting of the parailin hydrocarbons isWithdrawn'via line 133 controlled by valve 134 and is passed to acondenser where the vapors are condensed. The liquid extract phaseconsisting of Vthe selective Vsolvent and naphthene hydrocarbons iswithdrawn from the bottom of the extractor E26 via line 135 controlledbyvvalve |36 and is pumped by pump 131 through heater 138 intofractionating column 139 provided with heater mi) and reflux coolingcoil 141 where the naphthene hydrocarbons are distilled from theselective solvent and pass via line 142 controlled by valve m3 to acondenser where the hydrocarbons are condensed. The bottoms in thefractionating column 139 consisting of the selective solvent arewithdrawn via line 1M controlled by valve M5 and are pumped by pump M6through lline 151 into storage tank 129.

In the foregoing example, a bottoms toluene fraction of essentially100%vpurity was produced in fractionating column 24 representing all ofthe toluene in the original feed charged to the azeotropic distillation.When the vaporized azeotropic distillate consisting of the nonaromatichydrocarbons, methyl ethyl ketone and water from the fractionatingcolumn 24 was selectively absorbed in extractor 85 to remove the methylethyl ketone and water and the hydrocarbon vapors therefrom wereextracted in the vapor phase with the benzyl alcohol in the extractor|26, a parainic hydrocarbon overhead distillate was .producedrepresenting about of the feed stock which contained about 80% paramnsand .20% naphthenes, the paraflinic distillate having a gravity of 64 A.P. I. The bottom fraction in the extractor when separated from theselec- I0 tive solvent in fractionating column 139 had a. gravity of 54A. P. I. and was recovered in a yield of about 35%, containing about 80%naphthene hydrocarbons and about 20% paraiiin hydrocarbons.

The foregoing description of my invention is not to be taken as limitingmy invention but -only as illustrative thereof since many variations maybe made by those skilled in the art Without departing from the scope ofthe following claims.

I claim:l

1. A process for the treatment of a complex hydrocarbon fraction toseparate chemically similar hydrocarbon components therefrom from otherhydrocarbon components contained therein which ordinarily distill fromthe hydrocarbon fraction in the same temperature range as saidchemically similar hydrocarbon components distill therefrom whichcomprises distilling said complex hydrocarbon fraction in the presenceof a suicient amount of an azeotrope former to produce a vaporizedmixture consisting of at least one of the components contained in saidcomplex hydrocarbon fraction together with Asaid azeotrope former,thereby leaving at least one of the components contained in saidcomplexv hydrocarbon fraction in the residue, extracting said vaporizedmixture in the vapor state in an extraction zone with a liquid selectiveabsorbent adapted to absorb the azeotrope former in preference tothehydrocarbon vapors and separating a solution of said liquid absorbentand azeotrope former from said hydrocarbon vapors said azeotrope formerbeing an organic compound which is not readily separable from saidvaporized mixture of azeotrope formers and hydrocarbons by extractionwith water and said liquid absorbent being a substantially non-aqueouspolar organic compound different from the azeotrope former, saidabsorbent being readily separable from the extracted mixture of liquidabsorbentand dissolved azeotrope former.

2. A process for the treatment of a complex hydrocarbon fraction toseparate chemically similar hydrocarbon components therefrom from otherhydrocarbon components contained therein which ordinarily distill fromthe hydrocarbon fraction in the same temperature: range as saidchemically similar hydrocarbon components disbeing introduced into saidextraction zone in a direction countercurrent to said vaporized mixtureand separating a solution of said solvent and azaotrope former from saidhydrocarbon vapors said azeotrope former being an organic compound whichis not readily separable from said vaporized mixture of azeotropeformers and hydrocarbons by extraction with Waterand said liquidabsorbent being a substantially non-aqueous polar org-anic compounddiierent from the azeotrope former, said absorbent being readilyseparable from the extracted mixture of liquid absorbent and dissolvedazeotrope former.

3. A process for the treatment of a complex hydrocarbon fraction toseparate chemically similar hydrocarbon components therefrom from otherhydrocarbon components contained therein which ordinarily distill fromthe hydrocarbon fraction in the same temperature range as saidchemically similar hydrocarbon components distill therefrom whichcomprises distilling said complex hydrocarbon fraction in the presenceof a suicient amount oi an azeotrope former to produce a vaporizedmixture consisting of at least one of the components contained in saidcomplex hydrocarbon fraction together with said azeotrope former,thereby leaving at least one of the .components contained in saidcomplex hydrocarbon fraction in the residue, extracting saidvaporizedmixture in the vapor state 'in an extraction zone with apliquidselective absorbent adapted to absorb the azeotrope former in preferencetothe hydrocarbon components andv separating a, solution of said liquidabsorbent and azeotrope former from said'hydrocarbon vapors saidazeotrope former being an organic compound which is not readilyvaporized mixture of azeotrope formers and hydrocarbons by extractionwith water and said liquid absorb-ent being a substantially non--aqueous polar organic compound different from the azeotrope former, saidabsorbent being readily separable from the, extracted mixture of Yliquidabsorbent and dissolved azeotrope former, said liquid absorbent having aboiling point substantially higher than the boiling point of said-azeotrope former and distilling said Solution of liquid absorbent andazeotrope former to sepa-rate said liquid absorbent from said azeotropeformer.

A4. A process as in claim l in which said azeotrope former comprisesmethyl ethyl ketone and said selective absorbent comprises diethyleneglycol.

5. A process for the treatment of a hydrocarbon fraction containingtoluene and'non-aromatic hydrocarbons to separate toluene from thenon-aromatic hydrocarbons contained therein which ordinarily distillfrom said hydrocarbon fraction in the same temperature range as toluenedistills therefrom which `comprises distilling said hydrocarbonlfraction in the presence of a suliicient amount of methyl ethyl ketoneas azeotrope former to vaporize the non-aromatic hydrocarbons togetherwith the methyl ethyl ketone thereby leaving toluene in the residuesubstantially lcompletely separated from the l hydrocarbons other thantoluene, extracting said vaporized mixture in the vapor state in anextraction zone with .aliquid absorbent adapted to absorb the azeotropeformer in preference to the hydrocarbon vapors and separating a solutionof said liquid absorbent and azeotrope former from said hydrocarbonvapors said azeotrope former being an organic compound which is notreadily separable from said vaporized mixture of azeotrope formers andhydrocarbons by extraction with Water and Saidliquid absorbent being asubstantially*non-aqueous polar organic compound different from theazeotropev former, said separable from said tolue'ne distills therefromwhich comprises'disy vaporize the non-aromatic hydrocarbons togetherwith the methyl ethyl ketone thereby leaving toluene in the residuesubstantially completely separated from the hydrocarbons other thantoluene, extracting said vaporized* mixture .in the vapor state in anextraction zone with diethylene glycol to absorb said methyl ethylketone 'and separating a solution of said diethylene glycol and methylethyl ketone from said non-aromatic hydrocarbon vapors. 7. A process forthe treatment of a complex hydrocarbon fraction containing threedifferent types of hydrocarbons to separate chemically similarhydrocarbon components therefrom from other hydrocarbon componentscontained therein which ordinarily distill from the hydrocarbon fractionin the same temperature range as said chemically similar hydrocarboncomponents distill therefrom which comprises distilling said complexhydrocarbon fraction in the presence ofv a sufficient amount of anazeotrope former to produce a vaporized mixture containing two of saidcomponents contained in said complex hydrocarbon fraction together withsaid azeotrope former, thereby leaving one of said components containedin said complex hydrocarbon tracted hydrocarbon component and selectivesolvent from the other unextracted hydrocarbon component said azeotropeformer being an organic compound which is notl readily separable fromsaid vaporizedfmlxture of azeotrope formers and hydrocarbons byvextraction with water and said liquid absorbent being a substantiallynonaqueous polar organic compound different from the azeotrope former,said absorbent being readily separable from the extracted mixture ofliquid absorbent and dissolved azeotrope former.

8. A process for the treatment of a complex lhydrocarbonfraction-containing parailn, naphthene and aromatic hydrocarbons toseparate chemically similar hydrocarbon components therefrom from othervhydrocarbon componentscontained therein which ordinarily distill fromthe hydrocarbon fraction in the same temperature -range as saidchemically similar hydrocarbon components distilltherefrom whichcomprises distilling said complex hydrocarbon fraction in the presenceof a sufficient amount of an absorbent being readily separable from theextracted mixture of liquid absorbent and dissolved azeotrope former.

' 6. A process for the treatment of a hydrocarbon fraction containingtoluene and nonaromatic-hydrocarbons to separate toluene from thenon-aromatic hydrocarbons contained therein which ordinarily distillfrom said hydrocarbon fraction in the same temperature range asazeotrope former to produce a vaporized mixture containing paraiiin andnaphthene hydrocarbons together with said azeotrope former, therebyleaving aromatic hydrocarbons in the residue, ex-

tracting said vaporized mixture in ,the vapor state in an extractionzone with a liquid absorbent adapted to absorb the azeotrope former inpreference to the hydrocarbon components, separating a solution of saidliquid absorbent and azeotrope former from said hydrocarbon vapors,passing said hydrocarbon vapors in contact with a. selective solventadapted to extract the naphthene hydrocarbons whileleaving the parafnand dissolved azeotrope former.

9. A process as in claim 7 in which said selective solvent comprisesbenzyl alcohol. 10. A process as in claim 1 in which said selecv tivesolvent comprises a polyhydric alcohol.

11. A process as in claim 1, in which said varieotrope former comprisesa ketone selected from the group consisting of acetone and methyl ethylketone and said selective absorbent comprises an absorbent selected fromthe groupconsisting of glycols and alkyl ethers of glycols.

JOHN D. RI'I'I'ENHOUSE.

REFERENCES CITED The following references are of record in the Vle ofthis patent:

UNITED STATES PATENTS ,l

Date

Number Name 2,212,810 Field Aug. 27, 1940 2,265,220 Sullivan Dec. 9,1941 2,137,605 Derr ..-er Nov. 22, 1938 2,096,871 Atkins Oct. 26, 19372,008,955 Hammond July 23, 1935 2,050,513 Van Peski, et al Aug, 11, 19362,316,860 'Guinot Apr. 20, 1943 2,360,655 Deanesly Oct. 17, 1944 FOREIGNPATENTS Number `Country Date Great Braam c. A. August 22, 1940

